HUMAN INSULIN / GENETICALLY ENGINEERED INSULIN-
INSULIN is produced by ISLETS OF LANGERHANS CELLS OF PANCREAS.
This hormone regulates blood sugar levels.
Insulin was earlier extracted from the pancreas of slaughtered cattles and pigs. This was causing allergic reactions in some patients.
Insulin is synthesized as pro-hormone which needs to be processed to become active. Pro-insulin consists of A, C, AND B PEPTIDE CHAINS. In mature insulin, this C PEPTIDE is not present and it is removed by processing. If the gene for insulin is introduced in BACTERIAL CELL, a mature form of insulin cannot be obtained.
In 1983, Eli Lilly, an American company prepared two DNA sequences of A and B chains of human insulin and introduced them in E.coli cells to produce insulin chains, separately. These chains were extracted and combined by creating disulfide bonds to form human insulin.
IMPORTANT TO NOTE: Hakura et al in 1977 chemically synthesized DNA sequence for two chains A and B and separately inserted into two pBR 322 plasmid vector.
Insulin production by recombinant DNA technology is designed by Gilbert and Villokomaroff in 1978.
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